Process of making portland cement



April 21, 1931. R. D. cHEE'sMAN 1,802,196-

ROCESS OF MAKING PORTLAND CEMENT Filed Aug. 22, 1928 WITNESS INVENTOR X Y Pacav. Zw

ATTORNEY Patented Apr. 21, 1931` RICHARD D. CHEESMAN, 0F RALEIGH, N ORTH CAROLINA v PROCESS OF MAKING PORTLAND CEMENT Application led August 22, y19.28.. ik Serial No. 301,411.

My invention relates to a process of making Portland cement, and it consists in the steps hereinafter set forth and claimed.

An object of my invention is to provide a process by means of which a superior grade of Portland cement may be made which cement is capable of forming concrete of greater strength than the ordinary gradey of cement.

A further object is to provide a process which is applicable to various forms of grinding mills in ordinary use without the necessity of changing thestructure of such mills materially. A

A further object is to provide a process of making cement which can be carried out without material increase in cost over the ordinary process. y

Other objects and advantages will appear in thenew and novel features of the invention to be particularly pointed out in the appended claims. l

My invention is illustrated in the accompanying drawing which is a section through a tube mill of the type which may be used successfully in this process.

Portland cement is made by heating to incipient fusion or vitriiication an intimate mixture of an argillaceous substance such as clay or shale, and a calcareous substance such as limestone or marl, in which mixture the percentage of silica7 alumina and iron oxide bears to the percentage of lime the ratio approximately 1:2 which vitriied product does not slake with water but upon grinding forms an energetic hydraulic cement.

If Portland cement clinker is ground after being cooled without the addition of any foreign substance, the resultant cement shows a flash or quick set. The usual practice is to add approximately 3% of gypsum which acts as a retarder. VThe early strength qualities of Portland cement are directly proportioned to the amount of what is known as flour in the cement. The amount of flour in the cement depends on the extent of pulverizing or grinding. i

Considerable frictional heat is generated in the course of grinding. This is particularly noticeable in a closed grinding unit such as a tube-mill.y The temperature of the'cement will increasejas much as 300 degrees F. This causes the added gypsum to lose varying amounts of its water of crystallization. o As kthis vapor saturates the Aair in the grinding units beyondthe dew-point7 it condenses on thesuspended particles of pulverized clinlrer` reacting with'same and causing this reacted 'cement to lose` its ultimate hydraulic properties.` The potential strength of cement ground under these conditions is as lowas 75% of that of the original clinker. n Thisv saturated moisture condition also by reacting with the 'suspended cement particles causes a coating or deposit of cementitious material to form on the y grinding media thereby reducing the eliciency of the same.

Ther present invention involves the ventilating of the; grinding units whereby fresh air will be introduced so f* as toreduce the P moisture condition below dew-point. "In carrying out my'invention I mayvmakesuse` 0f 'a tube mill like Ythat shown in the drawing,V Thisconsists of a cylinder-.1 which is revolved 4 onqtrunnions 2 and by means of a drive c.

wheel 4. The cylinder is provided with partitions 5 and with the usual grinding balls 6. In order to cause a stream of air to pass through the tube mill I provide a suction fan 7 which is connected to a dust collector 8, the latter being connected by a pipe 9 with the hollow trunnion 3. At 10 I have shown adischarge chute having a rotary member 11. f

The material'is fed into the tube in the ordinaryway and during the grinding process heat is developed which, as stated, drives olf from the gypsum water of crystallization. The'air which passes through the tube collects this moisture and removes it and the cement flour passes through the` outlet'lO and past the rotating element 11 which, itwill be observed, permits the discharge of the cethe grinding operation. As stated above, this moisture tends to react with the suspended Earticles so as to cause them to lose their ydraulic properties. By getting rid of the moisture the original potential strength of the cement is preserved. Since the air is drawn in thro h the opposite end of the cylinder fnomthe ischarge pipe end and A,passes entirely through the cylinder any moisture liberated in any portion of the cylinder is taken up by the air and removed.

I claim:

1. The herein described process of Avproducin Port-land cement which consists in grinding Portland cement clinkers together with gypsum containing Water of crystallization and .removing the moisture liberated by the heat of the grinding operation.

2. The herein described rocess of producing Portland cement w ich consists in grinding Portland cement clinkers together with l.gypsum containing Water of crystallization and removing the moisture liberated by the heat ofthe grinding operation cont-inuou'sly during the grinding step.

3. The herein described process of produci Portland cement which consists in grinding Portland cement clinkers 'together with gy sum containing Water of crystallization and) in passing a. current of air through the grinding mechanism while the 'latter is in operation, thereb removing moisture liberated by the heat o the grinding step.

4. The herein described process of producin Portland cement which consists in grinding cement making material including sum 'having moisture therein capable of eing eliminated by the heat of .the grinding step and in removing the moisture thus y'liberated by a current of air.

RICHARD vD. CHEESMAN. 

